The present invention relates to sound processors and, more particularly, to a sound processor for producing simulated automobile or motorcycle engine sounds.
An enjoyable aspect of driving a 50""s, 60""s or 70""s classic automobile or motorcycle is the endearing and unique audible sound signature of that specific vehicle. The ability to produce these unique sounds in today""s automobiles is difficult due to new engine technology and the limitations imposed by government mandated pollution controls. New automotive designs have concentrated on reducing road and engine noise, placing the driver in a more serene and quiet environment. Enthusiasts who once enjoyed the unique rumble and throaty sounds of the 1960""s xe2x80x9cmuscle carsxe2x80x9d, such as a 327 Short Block Chevy, 427 Corvette, Ferrari, Dodge Hemi, or a Harley Davidson motorcycle, etc., cannot duplicate anything approaching these feelings in new automobiles.
The motivation of this invention is to return the joy and excitement of the 50""s, 60""s and 70""s era when classic hot rod sounds were trademarks and a pleasurable part of the driving experience. Imagine the pleasure of riding down the road in your modern automobile, but with the throaty sound of a 327 Short Block V8 or the rumble of a Harley Davidson motorcycle emanating from a xe2x80x98virtualxe2x80x99dual exhaust system.
The present invention takes the form of an automobile sound processor containing prerecorded or synthesized sound signatures of vintage automobiles and motorcycles or other sounds, along with other audio processing components, that is integrated with an automobile""s on-board stereo sound system. A mode selector on the automobile sound processor or the vehicle""s stereo system allows the user to select the desired classic car sound signature to be replicated. Sensors or transducers located in the engine compartment measure engine RPM and manifold vacuum. The sensors communicate instantaneous measurements of engine RPM and manifold vacuum to the sound processor and other audio processing components. The output of the sound processor is a composite audio replication of a selected sound signature. The sound signature is reproduced through the vehicle""s on-board stereo sound system and modulated by the driving dynamics of the driver""s car, as if the car were producing these sounds by responding to acceleration and deceleration dynamics.
The automobile sound processor includes a sound memory with one or more look-up-tables (LUT) programmed with unique broadband and high dynamic range sound signatures from various classic automobiles and/or motorcycles. The sound signatures could have been recorded from actual classic cars over an operating range from idle to maximum RPM. Each sound signature at each recorded RPM consists of a short temporal period that when continuously replayed sounds smooth and continuous.
Preferably, the automobile sound processor is adapted to replicate actual engine sounds under three conditions: 1) no-load, 2) loaded acceleration and 3) deceleration. The engine loading, as detected by the manifold vacuum sensor is used to modulate an audio filter that processes the output of the audio processor to change the tonal character of the sound signature thus reflecting the audible changes characteristic of the strain of the engine. If the engine is under load, the vacuum will decrease and the audio filter will accentuate low frequencies while suppressing some of the higher frequencies of the sound signature. Alternatively or in addition, the engine operating conditions may be sensed by calculating a derivative of the engine RPM to determine acceleration and deceleration. If the engine is braking the vehicle""s speed, such as when downshifting to slow the vehicle, the vacuum will increase and the audio filter will accentuate higher frequencies and suppress the lower frequencies. Under no-load situations, the audio filter will add no frequency filtering. The stereo output of the audio filter is passed to the audio inputs of the vehicle""s stereo amplifier and then to the vehicle""s speaker system.
In an alternative configuration, the sound memory includes either two or three look-up-tables containing sound signatures of an engine under different operating conditions, including loaded accelerating conditions, no-load conditions and/or decelerating conditions. The vehicle engine operating conditions are determined by manifold vacuum, by the derivative of the engine RPM and/or by an accelerometer, and the corresponding sound signature is chosen from the sound memory and processed by the audio processor. In one preferred embodiment, sound signatures are chosen from a first look-up-table and a second look-up-table and electronically summed together to produce a blended sound signature representing the sound of the engine under current operating conditions. In addition, the sound processor may use selective audio filtering to alter the tonal character of the sound signature.